Air blast circuit breaker



Aug- 2 1966 H. FORWALD 3,264,440

AIR BLAST CIRCUIT BREAKER Filed March 27, 1964 United States Patent O 3,264,440 AIR BLAST CHRCUIT BREAKER Haakon Forwald, Ludvika, Sweden, assignor to Allmnna Svenska Elektriska Aktiebolaget, Vasteras, Sweden, a Swedish corporation Filed Mar. 27, 1964, Ser. No. 355,154

Claims priority, application Sweden, Apr. 10, 1963,

3,97 6/ 63 3 Claims. (Cl. 20d-148) This invention relates to air blast circuit breakers, and more specifically relates to an air blast circuit breaker interrupter structure having two series connected breaking contacts, one of which 'has a parallel connected resistor wherein both of the contacts are subjected to a strong effective blast of extinguishing air.

Interrupters lfor gas blast circuit breakers are well known to the art and 'are usually provided with parallel connected resistors yfor keeping the voltages across the interrupting contacts within reasonable limits during interruption. The provision of a parallel connected resistor then requires a second series connected pair of contacts which will operate to break the resistor current after extinction of the main arc.

With such arrangements it is very difficult to obtain an effective blast of extinguishing gas for both the main and resistor contacts while, at the same time, maintaining the desired function of the main contacts.

In accordance with the present invention, the two sets of series connected contacts are carried within a container which is permanently iilled with compressed gas wherein each movable contact is hollow and conducts a ow of compressed air therethrough under the control of a common blast valve. This blast valve .then serves the dual function of a control valve for the operation of one of the pairs of contacts responsible for interrupting the resistor current, with .the main interrupting contacts being opened only long enough to interrupt the 'arc kand being thereafter closed with the resistor contacts remaining open to serve as an isolating contact for the system.

Moreover, and as indicated previously, both the main contacts and resistor contacts .are subjected to an extremely powerful tiow of extinguishing a-ir during their operation.

In reclosing the interruptor, that contact now serving as an isolating con-tact, and which was responsible Ifor the interruption of the resistor current, is closed. Thus, the function of opening the circuit and closing the circuit is distributed between the two contacts, whereby contact wear is decreased and the breaking capacity of the interrupter is increased.

Accordingly, a primary object of this invention is to provide a novel gas blast interrupter structure having series connected interrupter contacts.

Another object of this invention is to provide `a pai-r of series connected contacts in a container which is permanently fil-led with compressed air, in which one of the contacts is connected in parallel with a resistor, and in which a .gas blast for each of the contacts is provided through la common blast valve.

Still another object of this invention is to provide a novel contact arrangement [for gas blast internupters wherein the contact which interrupts resistor current further serves `as 'an isolation contact ifor the circuit so that the main interrupting contact is immediately reclosed after interruption.

These and other objects of this invention will become apparent from the following description taken in connection |with the drawing which shows a cross-sectional view of an interrupter structure constructed in accordance with the present invention.

3,264,44@ Patented August 2, 1966 ICC Referring now to the drawing, the air blast circuit breaker shown therein includes a metal interrupter container 1 which is permanently lilled with compressed air. The container 1 is supported atop a hollow insulator column 2 which is carried from a grounded compressed air container A3. The compressed air yfrom container 3 is in continuous communication with the interior of housing 1 through the hollow interior of insulator 2.

The container `1 then carries two series conected breaking gaps. The lirst breaking gap includes a stationary contact 5 which is supported by a lead-through bushing insulator 6 which passes through the wall of the container 1. The second pair of breaking gaps includes the stationary contact 7 which is carried at the end of lead-through bushing insulator -8 which passes through the wall of container \1.

A resistor 4 is then connected in parallel with 4the pair of contacts which includes stationary contact 5, one end of resistor 4 being connected to the container 1, Iwhile the upper end is conected to terminal 6a which serves as one terminal .for the circuit breaker. The other terminal .for the circuit breaker clearly will -be terminal 8a at the end of |bushing insulator 8 and connected to contact 7.

The movable contacts `for the two series connected breaking gaps are each electrically connected to housing 1 and include the hollow contacts 9 and 10 which each communicate with space 11. The space 11 may communicate with the outer assembly atmosphere by means of channels 12. An air blast valve 13 is arranged to enclose channels 12 'when the contacts 9 and 10 .are closed, and engage their respective stationary contacts 5 and 7.

A piston 14 is carried by the movable hollow contact 9, and one side of piston 14 is exposed to the compressed air pressure in container 1, while its other side is inuenced by the pressure within space 15. Space 15 is in permanent communication with space x11 through the channel 16. -A spring 417 biases hollow contact 9 into engagement with stationary contact 5 when the pressures on the opposite sides of piston 14 are equal.

The hollow contact 10' is connected to a piston 1S which has one side in communication with the `pressure within container 1, while its other and left-hand side is exposed to the pressure within space 19.

A control valve 20 is arranged for selectively connecting space 19 to the pressure within container 1 through chanf nel 21, or to the open air through channel 22 when valve 20 is moved to the right. A spring 23 biases movable hollow contact 10` into eng-agement with stationary contact 7.

Control valve 20 is moved by a piston 24 connected thereto whichis normally held in the left-hand position shown :by biasing spring 25. Piston 24, which is carried in a suitable cylinder has its left-hand surface in commun-ication with conduit 26 which extends into cylinder 27. The cylinder 27 carries a piston 28 which is connected to blast valve 13.

The blast valve 13 is normally closed by means of spring 29 which seats on the right-hand side of piston 28. The piston 2S has openings therethrough which are provided with non-return valve members 3), whereby air flow may occur through the openings in piston 28 from space 27 through the piston surface, although it cannot occur in the reverse direction since valves 30 will then close.

A very narrow leakage channel 31 is formed in piston 28. An air control conduit 32 extends upwardly from grounded container 3 with air pressure being selectively applied to conduit 32 by means of a control valve 33. The conduit 32 extends upwardly and into communication with the left-hand surface of piston 28.

The operation of the structure shown in the drawing is as follows: In order to open the air blast circuit breaker contacts, the valve 33` is operated to apply compressed air to conduit 32. This lls the space to the left of piston 28 with compressed air to open blast valve 13. The space 11 is then emptied of compressed .air through channels 12 so that the space 15 below piston 14 is also vemptied of compressed air. The pressure' in container 1 lthen forces the hollow contact 9 downwards so that the main breaking gap contacts and 9 open with a strong blast of compressed air playing on the arc drawn between the contacts.

When the air blast valve 13 reaches its fully open position, compressed air from conduit 32 can now ow into conduit 26 whereby piston 24 is moved to the right. Therefore, the control valve 20 will shut off channel 21 and open channel 22 so that space 19 is vented to the open air. Piston 18 is thus forced to the left together with the hollow contact by means of the pressure in container 1, whereby the second breaking gap including contacts 7 and 10 are opened. This operation occurs after contacts 5 and 9 have extinguished the main larc so that contacts 7 and 10 extinguish only the current owing through resistor 4. Moreover, the breaking gap including contacts 7 and 10 is exposed to a powerful blast of high pressure gas so that, even if the resistor current is high, it will be eiiciently extinguished.

During the actual breaking action, the compressed air or gas will flow continuously from the space .to the left of piston 28 to the space to the right of the piston through the narrow channel 31 in piston 28. Thus, pressure is gradually equalized on the two sides of the piston so that it will eventually return to its left-hand position under the action of the spring 29 to automatically reclose blast valve 13. Once the blast valve 13 closes, the space 11 is rapidly filled with compressed air through the hollow contacts so that the space will be brought up `to the same pressure as that on the other side of piston 14. The hollow contact 9 will then be reclosed by spring 17 with only the hollow contact 10 remaining in the open position, since Vthe control valve is still in its right-hand end position. Therefore, the contacts 7 and 10 serve as the isolating contact for the system.

In order 4to close the circuit breaker, the valve 33 is operated to vent conduit 32 to open air. The space to the left of piston 24 is thereby rapidly emptied through conduit 26 and the non-return valves 30. Spring 25 will then move control valve 20 to the left so that the space 19 behind piston 18 is once again connected to the pressure of the air in container 1. The same pressure is thus obtained on both sides of piston 18 so that spring 23 returns contact 10 to the closed position for reclosing the circuit connected between terminals 6a 'and 8a.

With the foregoing structure, it is seen that the opening and closing operatio-ns are divided between contact pairs 9 Aand 5, and 7 and 10, respectively. Thus, wear on the contacts is more evenly distributed. At the same time, contacts 7 and 10 serve as isolating contacts, thus eliminating the need for auxiliary isolating switches.

It is possible to arrange the structure of the drawing so that both gaps will open simultaneously. More specically, with the present invention, `the conduit 26 is connected to cylinder 27 in such a way that contacts 5 and 9 will open before contacts 7 and 10. If, however,

conduit 26 is connected directly to conduit 32 instead of through the operating piston 28 off the blast valve, both contact pairs will be simultaneously operated for superior breaking operation for short line faults.

Moreover, with this type of operation, the load on the resistor is decreased so that the resistor can be made smaller.

Although this invention has been described with respect to its preferred embodiments, it should be understood that many variations and modifications will now |be obvious to those skilled in the art, and it is preferred, therefore, that the scope of the invention be limited not by the specific disclosure herein but only by the appended claims.

The embodiments of the invention in which anexclusive privilege or property is claimed are delined as follows:

1. A gas blast circuit breaker interrupter structure comprising a conductive housing, a high pressure gas supply permanently connected to said conductive housing to maintain the interior of said conductive housing at high pressure, iirst and second stationary contacts supported on the interior of said conductive housing and in insulated relation with respect to each other and to said conductive housing, first and second hollow movable contacts positioned within said conductive housing normally engaging said iirst and second stationary contacts, and mounted for movement out of engagement therewith, a resistor permanently electrically connected between said first stationary contact and said first movable contact, and a blast valve in the wall of said container; said second contacts being connected in series with said rst contacts; said lirst and second hol-low contacts defining respective flow paths from interior portions of said conductive housing to the interior surface of said blast valve whereby high pressure gas flows through said first and second hollow movable contacts when said blast valve is opened; and an operating means connected to said first and second hollow movable contacts for moving said rst and second hollow contacts between engaged and disengaged positions with respect to said first and second stationary contacts respectively.

2. The device substantially as set forth in claim 1 wherein said operating means includes time delay means connected to said second movable contact for delaying movement thereof to its said disengaged position until said first movable contact is moved to its said disengaged position.

3. The device substantially as set forth in claim 2 wherein said operating means further includes reclosing means connected to said first contact for automatically reclosing said rst contact immediately after its movement to its said disengaged position.

References Cited by the Examiner UNITED STATES PATENTS l/l954 Forwald 200-148 3/1961 Baker 200-148 

1. A GAS BLAST CIRCUIT BREAKER INTERRUPTER STRUCTURE COMPRISING A CONDUCTIVE HOUSING, A HIGH PRESSURE GAS SUPPLY PERMANENTLY CONNECTED TO SAID CONDUCTIVE HOUSING TO MAINTAIN THE INTERIOR OF SAID CONDUCTIVE HOUSING AT HIGH PRESSURE, FIRST AND SECOND STATIONARY CONTACTS SUPPORTED ON THE INTERIOR OF SAID CONDUCTIVE HOUSING AND IN INSULATED RELATION WITH RESPECT TO EACH OTHER AND TO SAID CONDUCTIVE HOUSING, FIRST AND SECOND HOLLOW MOVABLE CONTACTS POSITIONED WITHIN SAID CONDUCTIVE HOUSING NORMALLY ENGAGING SAID FIRST AND SECOND STATIONARY CONTACTS, AND MOUNTED FOR MOVEMENT OUT OF ENGAGEMENT THEREWITH, A RESISTOR PERMANENTLY ELECTRICALLY CONNECTED BETWEEN SAID FIRST STATIONARY CONTACT AND SAID FIRST MOVABLE CONTACT, AND A BLAST VALVE IN THE WALL OF SAID CHAMBER; SAID SECOND CONTACTS BEING CONNECTED IN SERIES WITH SAID FIRST CONTACTS; SAID FIRST AND SECOND HOLLOW CONTACTS DEFINING RESPECTIVE FLOW PATHS FROM INTERIOR PORTIONS OF SAID CONDUCTIVE HOUSING TO THE INTERIOR SURFACE OF SAID BLAST VALVE WHEREBY HIGH PRESSURE GAS FLOWS THROUGH SAID FIRST AND SECOND HOLLOW MOVABLE CONTACTS WHEN SAID BLAST VALVE IS OPENED; AND AN OPERATING MEANS CONNECTED TO SAID FIRST AND SECOND HOLLOW MOVABLE CONTACTS FOR MOVING SAID FIRST ANS SECOND HOLLOW CONTACTS BETWEEN ENGAGED AND DISENGAGED POSITIONS WITH RESPECT TO SAID FIRST AND SECOND STATIONARY CONTACTS RESPECTIVELY. 